Mineral lubricating oils containing trisalkylpyridine molybdenum tricarbonyl compounds



United States Patent 3,118,840 MINERAL LUBRICATTN G OILS CON TAIN ENG IRES- ALKYLPYRIDTNE MQLYBDENUM TRECARBON- YL CUMPOUNDS Edwin L. De Young, Milwaukee, Wis, assignor to fitandard Oil Company, Chicago, IlL, a corporation of Indiana No Drawing. Filed Dec. 19, 1960, Ser. No. 76,472 5 Claims. (Cl. 25233.4)

This invention relates to novel oil-soluble organo-molybdenum co-ordination compounds as new compositions of matter, and to compositions containing the same, which compositions possess corrosion and/or oxidation inhibiting properties. More particularly, it concerns novel oilsoluble alkyl substituted pyridine molybdenum carbonyl co-ordination compounds and their use as additives to lubricants to impart anti-oxidation characteristics thereto.

Within recent years it has become common practice to impart improved properties to lubricants through the use of various types of additives or addition agents. Lubricating oils employed in internal combustion engines such as automotive and diesel engines require the use of one or more addition agents to improve their serviceability under certain adverse operating conditions. Among the more important additives employed are type which function to prevent the formation and accumulation of sludge and varnish-like coatings on pistons and cylinder walls of the engine. Such additives which have the property of maintaining clean engines are referred to as detergent-type lubricant additives. The more effective addition agents which have been developed for compounding with lubricants are many sulfur-containing organic compounds such as, by way of example, sulfurized terpenes, sulfurized hydrocarbon oils, vegetable oils or animal oils, organic polysulfides, particularly polyalkyl polysulfides, metal salts of organo-substituted thioacids of phosphorus, metal salts of the reaction product of a phosphorus sulfide and a hydrocarbon such as, for example, polybutenes and other polyolefins, and combinations of the foregoing.

Corrosion inhibitors also play an important part in the formulation of efiicient lubricants. Such corrosion inhibitors should effectively inhibit the corrosion of metal alloys of the type used in engine bearings and other engine parts. Recent increased use of silver and similar metals in the construction of improved internal combustion engines has created new problems in the use of sulfur-containing additives in lubricants for such engines; the primary problem created being the corrosion of such silver parts of the engine by the sulfur-containing additives. While such corrosion can be eliminated by avoiding the use of sulfur-containing additives in lubricants for such engines, this solution of the problem is accompanied by the loss of the highly desired beneficial effects of the additives of this type.

An object of the present invention is to provide novel oil-soluble organo-molybdenum co-ordination compounds and a method of preparing the same. Another object is to provide novel oil-soluble organo-molybdenum co-ordination compounds having particular utility as lubricant additives. A particular object is to provide novel oilsoluble alkyl substituted pyridine molybdenum carbonyl co-ordination compounds which have anti-oxidative properties in addition to having substantial metal corrosion inhibiting properties when added to mineral lubricating oils. A further object is to provide a composition which will inhibit the corrosion of silver and similar metals by sulfur and/ or organic sulfur-containing compounds. Still another object is to provide a method of inhibiting the corrosion of engine parts in contact with lubricant compositions Which contain sulfur and/ or organic sulfur-containing compounds which are normally corrosive to metals.

Other objects and advantages of the present invention will become apparent from the ensuing description thereof.

it has been discovered that certain novel oil-soluble alkyl substituted pyridine molybdenum carbonyl co-ordination compounds have anti-oxidant and/ or anti-corrosion properties. Such compounds are extremely useful as additives for lubricants which are normally corrosive to metals with which such lubricants are in contact. Thus, in accordance with the present invention, the oil-soluble molybdenum carbonyl co-ordination compounds are prepared by reacting molybdenum hexacarbonyl with an alkyl substituted pyridine having at least one alkyl substituent containing at least four carbon atoms. The reactants being employed in the molar ratio of about one mole of molybdenum hexacarbonyl to about three moles of the alkyl substituted pyridine, preferably with a slight excess of the pyridine reactant. The reaction is carried out at atmospheric pressure and at temperatures of from about C. to about C. Depending upon the temperatures employed, the reaction time may vary from about two hours to about 16 hours.

The new products are viscous liquids of varying oil solubility depending upon the amount and nature of hydrocarbon substitution in the structure and nature of the base oil. They have particular value as anti-oxidants for lubricating oil lubricants, as hearing corrosion inhibitors and, because they are non-corrosive to silver in lubricant compositions, have a wide range of applicability. In general, it is desirable that the molybdenum carbonyl co-ordination compounds contain at least four carbon atoms, preferably 8 to 18 carbon atoms, in the monoalkyl or polyalkyl substituted pyridine reactant in order to provide adequate oil solubility. The products then can be handled in the form of mineral oil concentrates which facilitate handling in the formulation of commercial lubricating oils and greases. The level of use in the finished lubricant, however, is usually quite small. For use as a oxidation in hibitor in a hydrocarbon oil susceptible to oxidative deterioration the concentration of the additive should be at least 0.2% by weight. Amounts above 0.5% give satisfactory results, but since such results may be obtained with lesser amounts, it is usually not economical to employ more than 0.5%.

In commercial formulation, the substituted pyridinemolybdenum carbonyl compounds will ordinarily be used, as is customary in conjunction with other compatible lubricating oil additives, for example, pour depressants, viscosity index improvers, anti-rust agents, anti-foam agents and the like. The base may comprise any hydrocarbon oil subject to oxidative deterioration. For most applications, the oil will comprise a mineral oil fraction of the usual lubricating oil range.

The new oil-soluble organo-molybdenum co-ordination compounds of the present invention are the co-ordination reaction products of molybdenum hexacarbonyl and an alkyl substituted pyridine, which co-ordination reaction products have the general formula R Mo(CO) wherein R is a pyridine radical having at least one alkyl substituent containing at least four carbon atoms.

The alkyl substituted pyridine employed in preparing the molybdenum carbonyl co-ordination compounds can be mono or poly, straight or branched, chain alkyl substituted pyridines. Examples of suitable pyridines are: butylpyridine, cyclopentylpyridine, hexylpyridine, octylpyridine, nonylpyridine, dodecylpyridine, hexadecylpyridine, octadecylpyridine.

The invention will be further illustrated by means of specific examples. In the examples, the new additives were evaluated by means of a modified stirring sand corrosion test (MSSCT) and the modified EMD silver bearing corrosion test.

The MSSCT test was run as follows: A copper-lead test specimen is lightly abraded with steel wool, washed with naphtha, dried and Weighed to the nearest milligram. The cleaned copper-lead test specimen is suspended in a glass beaker, cleaned with a hot tri-sodium phosphate solution, rinsed with water, acetone and dried, and 300 grams of the oil to be tested, and 50 grams of a 3035 mesh sand charged to the beaker. The beaker is then placed in a bath or heating block and heated to a temperature of 330 F. (:2" F.) while the contents are stirred by means of a stirrer rotating at 1300 r.p.m. The contents of the beaker are maintained at this temperature for forty-eight hours, after which the copper-lead test specimen is removed, rinsed with naphtha, dried and weighed. The test specimen is then replaced in the beaker and the test continued for another twenty-four hours (seventy-two hours total). At the conclusion of this time, the test specimen is removed from the beaker, rinsed with naphtha, dried and weighed.

In the modified EMD test a silver strip 2 cm. x 5.5 cm. with a small hole at one end for suspension is lightly abraded with No. steel wool, wiped free of any adhering steel wool, washed with carbon tetrachloride, air-dried and then weighed to 0.1 milligram. Three hundred cc. of the oil to be tested is placed in a 500 cc. lipless glass beaker and the oil is heated to a temperature of 300 F. (12 F.) and the silver test strip suspended in the oil so that the strip is completely immersed therein. The oil in the beaker is stirred by means of a glass stirrer operating at 300 r.p.rn. At the end of twenty-four hours, the silver strip is removed and while still hot rinsed thoroughly with carbon tetrachloride and air-dried. The appearance of the strip is then visually noted and given ratings according to the following scale:

1Bright 2-Stained 3--Grey-black 4-Black, smooth 5Black, flake After the visual inspection the silver strip is immersed in a potassium cyanide solution at room temperature until the silver surface assumes its original bright or silver appearance. The silver strip is then washed successively with distilled water and acetone, air dried and weighed. A weight loss of 20 mg. or less is considered passing.

Example I A charge of 88 grams (0.33 mole) of molybdenum hexacarbonyl and 205 grams (1.0 mole) of 4-(l-butylpentyl) pyridine was placed in a glass reaction vessel equipped with a stirrer and thermometer. The reaction mixture, at atmospheric pressure, was heated to 120 C. and held for six hours. The product, a thick orange-red syrup, analyzed 11.7% molybdenum and 4.75% nitrogen. Calculated for tris [4-(1-butylphentyl) pyridine] molybdenum carbonyl: 12.0% molybdenum and 5.28% nitrogen.

The product was tested at the 0.5% concentration level in solvent extracted SAE 40 grade Mid-Continent oil containing about 3% calcium petroleum sulfonate and about 1.25% calcium sulfide phenate. The oil gave a bright EMD silver strip and MSSCT weight losses of 171 mg. at 48 hours and 321.6 mg. at 72 hours; whereas the same oil without the product of this example gave a MSSCT loss of 870.4 mg. at 48 hours.

Example II A solvent extracted SAE 30 grade Mid-Continent oil containing about 3% of a detergent of the neutralized phosphorus sulfide-polybutenes reaction product type gave 752.4 mg. weight loss at 48 hours. When 0.5% of the product from Example I was added to the above oil the MSSCT losses were 252.7 mg. at 48 hours and 463.5 mg. at 72 hours.

4 Example III A 40 SAE, 63 VI, grade Mid-Continent oil gave MSSCT loss of 740.9 mg. at 48 hours. When 0.25% and 0.5% of the product from Example I was added to the above oil the MSSCT losses were 102.1 mg. at 48 hours and 298.0 mg. at 72 hours, and 129.3 mg. at 48 hours and 214.4 mg. at 72 hours respectively.

Example IV The product of Example I was tested at 0.1% and 0.25% concentration level in solvent extracted SAE 30 grade Mid-Continent oil containing about 2.8% of a detergent of the barium neutralized phosphorus sulfide-polybutene reaction product type. The oil gave a bright EMD silver strip and MSSCT weight losses of 772.5 mg. at 48 hours, 90.9 mg. at 48 hours and 169.7 mg. at 72 hours respectively.

Example V The product was tested at 0.5 concentration level in solvent extracted SAE 30 grade Mid-Continent oil containing about 3% of a detergent of the borated barium neutralized phosphorus sulfide-polybutene reaction product type. The oil gave a bright EMD silver strip and MSSCT weight losses of 49.5 mg. at 48 hours and 152.0 mg. at 72 hours.

The above described molybdenum carbonyl compounds can be used in combination with lubricant base oils, such as hydrocarbon oils, synthetic hydrocarbon oils, such as those obtained by the polymerization of hydrocarbons, such as olefin polymers, for example, polybutenes, polypropylene and mixtures thereof, etc.; synthetic lubricating oils of the alkyleneoxide type, for example, the Ucon oils, marketed by Carbide and Carbon Corporation, as well as other synthetic oils, such as the polycarboxylic acid estertype oils, such as the esters of adipic acid, sebacic acid, maleic acid, azelaic acid, etc.

While this invention has been described in connection with the use of the herein-described additives and lubricant compositions, their use is not limited thereto; but the same can be used in products other than lubricating oils, such as for example, fuel oils, insulating oils, greases, non-drying animal and vegetable oils, waxes, asphalts, and any fuels for internal combustion engines, particularly where oxidation must be cornbated.

Concentrates of a suitable oil base containing more than 10% and up to about of the oil-soluble alkyl substituted pyridine molybdenum carbonyl compound alone or in combination with other additives can be used for blending with hydrocarbon oils or other oils in the proportions desired for the particular conditions of use to give a finished product containing at least 0.2% of the molybdenum carbonyl.

Percentages given herein and in the appended claims are weight percentages unless otherwise stated.

Subject matter disclosed but not claimed in herein is being claimed in divisional application S.N. 138,216, filed September 7, 1961.

Although the present invention has been described With reference to specific preferred embodiments thereof, the invention is not to be considered as limited thereto but includes Within its scope such modifications and variations as come within the spirit of the appended claims.

I claim:

1. A mineral lubricating oil containing from about 0.2 to about 0.5 of an oil-soluble organo-molybdenum tricarbonyl compound having the formula R Mo (CO) wherein R is pyridine mono-substituted by alkyl of 418 carbon atoms.

2. A mineral lubricating oil containing from about 0.2 to about 0.5% of tris-(nonylpyridine) molybdenum tricarbonyl.

3. A mineral lubricating oil containing from about 0.2 to about 0.5 of tris-[4-(1-butylpentyl) pyridine] molybdenum tricarbonyl.

4. An additive concentrate suitable for addition to a mineral lubricating oil to impart oxidation stability to said oil consisting essentially of a mineral lubricating oil containing from about 10 to about 90% of an oil-soluble organo-molybdenum tricarbonyl compound having the formula R Mo(CO) wherein R is pyridine mono-substituted by alkyl of 418 carbon atoms.

5. A lubricating oil composition having improved oxidation stability comprising: (a) a major amount of mineral lubricating oil base; (b) 0.5% of tris[4-(1-butylpen tyl) pyridine] molybdenum tricarbonyl; (c) 3.0% of ca1- cium petroleum sulfonate; and (d) 1.25% of calcium sulfide phenate.

References Cited in the file of this patent UNITED STATES PATENTS Fischer et a1.: Chem. Ber., vol. 93, pp. 1156-61 (1960) 

1. A MINERAL LUBRICATING OIL CONTAINING FROM ABOUT 0.2 TO ABOUT 0.5% OF AN OIL-SOLUBLE ORGANO-MOLYBDENUM TRICARBONYL COMPOUND HAVING THE FORMULA R3MO(CO)3 WHEREIN R IS PYRIDINE MONO-SUBSTITUTED BY ALKYL OF 4-18 CARBON ATOMS. 